It's helpful to know how to start tracking files already in git using git lfs.

The tip in the README is only partial (as are several answers on Stack Overflow):

Tip: if you have large files already in your repository's history, git lfs track will not track them retroactively. To migrate existing large files in your history to use Git LFS, use git lfs migrate.

I found the answer by @bk2204 here:

If you want to track existing files, you need to either use git lfs migrate import --no-rewrite with an appropriate pattern or use git add --renormalize . after git lfs track (and then commit).

The git add --renormalize . made all the difference 👍 thanks! 🙏